I have a 1999 motorhome with a 6.5 turbo in it. For a while now when I go to start it after glow plugs warmed the starter just clicks and then when I try it again it starts like normal. I have checked all the grounds the best I could and see no apparent problem. Have newer batteries and always charged. I was thinking it might be the switch or the solenoid, but not sure how to determine. It has not left me stranded, but always wondering when it will. I have had this unit since it was new and the original starter is still in it. There is 98,000 miles on it and I completely rebuilt and balanced the engine at 70,000. Any suggestions would be appreciated